The ECG is a diode ladder filter and uses 6 x red LEDs for the diodes. Diode ladder filters have a different sound to transistor ladder filters, and if you’re gonna use diodes, why not use LEDs and get a free light show too – the LEDs will brighten as you turn up the cutoff of the filter, or when a CV is applied. For maximum visual effect ECG is mounted on a translucsuent red acrylic panel. ECG is based on my Vogue VCF/VCA, the inspirations for the changes to diode ladder the Roland TB303 filter.